The subject matter of the present invention relates generally to pressure tank connectors for transmitting a pressurized fluid, which may be liquid or gas, into or out of a tank through an opening surrounded by such connector. More particularly, the pressure tank connector of the present invention is designed to function as an auxiliary safety valve when the pressure within the tank exceeds a safe value, thereby preventing tank explosions.
The safety connector of the present invention is particularly useful on pressurized air tanks used on trucks and other vehicles for operating air brakes. Previously, air brake tanks have exploded due to overpressure conditions caused when the main safety valve in the line to the tank has either been damaged or frozen shut in cold weather. The resulting explosion has caused death and serious injury to many truck drivers.
In the past, pressure tank connectors have usually been separate members which are welded into an opening in the tank wall. As a result of use of such welded connectors, the tanks often explode during overpressurized conditions, usually in the vicinity of the weld. This problem has been overcome by the present invention, which forms the safety connector integral with the cylindrical side wall portion of the tank. Thus, when the tank expands slightly during an overpressurized condition, the safety connector is deformed from its normal annular shape into a slightly oblong configuration. This causes the pressurized fluid within the tank to slowly leak out of the tank through the resulting space formed between the threaded portion of the connector and the external fitting threaded into such connector.
Previously it has been known to form pressure tank connectors integral with the tank wall at the top end of the tank, such as the liquefied petroleum gas tank, shown in U.S. Pat. No. 3,152,718 of Weatherhead. However, these connectors are formed in the hemispherical end of the tank and are not provided on the cylindrical side wall portion. As a result, such integral connectors do not function as auxiliary safety valves in the manner of the present invention because they do not deform when the tank expands in overpressurized conditions.
The safety connector of the present invention, formed integral with the cylindrical side wall of the tank, was compared in tests with similar tanks having the same connector formed in the hemispherical end of the tanks. The result was that all four tanks having safety connectors formed integral with the cylindrical side wall, in accordance with the present invention, acted as auxiliary safety valves and relieved pressure within the tank gradually when the tank pressure reached about 700 psi. This is approximately five times the normal operating pressure of the tank, which is 120 psi. However, when four other tanks having the connector formed integral with their hemispherical ends were tested, each tank ruptured and exploded at pressures of 925, 950, 975, and 1125 psi, respectively. The fourth tank ruptured at a higher pressure because it was formed of drawn metal while the others were formed of welded sheet metal. Nowhere is this safety valve feature suggested in the previous patent and the above-mentioned tests prove that an integral connector does not inherently operate this way when positioned on the hemispherical end of the tanks.